1. Technical Field
The present invention relates to a printer for printing on a print medium.
2. Background Arts
Generally, known is a printer with a mechanism in which a print sheet picked-up from a sheet supply tray is fed to a print unit having inkjet heads and so on by a pair of registration rollers. In such a mechanism, a pint sheet is stalled in a state where its leading edge is contacted to a registration nip between the registration rollers to slack the print sheet, so that an oblique feed of the print sheet can be compensated. Then, the registration rollers are driven to feed the print sheet to the print unit.
When the print sheet is fed forward by the registration rollers, the slack of the print sheet is expanded (i.e. back tension is applied to the print sheet) between the registration nip of the registration rollers and their upstream rollers. As a result, a noise (sheet expansion noise) may be generated due to the expansion of the slack.
A Japanese Patent Application Laid-Open No. 2010-215389 (Patent Document 1) discloses a printer in which an assistant operation is carried out. In the assistant operation, upstream rollers located upstream from the registration rollers are driven while registration rollers are being driven in order to reduce the above-explained sheet expansion noise, so that noise suppression is improved. In addition, feeding failures can be also reduced according to the assistant operation, so that feed performance is improved.
The printer disclosed in the Patent Document 1 includes sheet supply trays disposed at a lower portion of the printer, and a sheet supply side-tray that is partially exposed to the outside of the printer. When supplying a print sheet from one of the sheet supply trays, a print sheet fed out from the sheet supply tray by rollers is received by intermediate feed rollers (corresponding to the above-explained upstream rollers), and the intermediate feed rollers feed it to registration rollers. The print sheet fed from the intermediate feed rollers is stalled in a state where its leading edge is contacted to a registration nip between the registration rollers, so that a slack of the print sheet is formed. Then, the intermediate feed rollers start the assistant operation at the same time when the registration rollers start to be driven. In the assistant operation, the intermediate feed rollers are driven in synchronization with the registration rollers. According to the assistant operation, the intermediate feed rollers and the registration rollers feed the print sheet while they maintain the slack of the print sheet. At a time when a trailing edge of the print sheet has passed through the intermediate feed rollers, the intermediate feed rollers finish the assistant operation.
On the other hand, when supplying a print sheet from the sheet supply side-tray, a print sheet fed out from the sheet supply side-tray by primary supply rollers (corresponding to the above-explained upstream rollers) is received by the registration rollers. The primary supply rollers start an assistant operation at the same time when the registration rollers start to be driven, and then finish the assistant operation at a specific timing. As explained above, the primary supply rollers feed a print sheet out from the sheet supply side-tray, and then feed it to the registration rollers. In order not to feed a next print sheet out from the sheet supply side-tray erroneously by the primary supply rollers, the primary supply rollers are not are driven in synchronization with the registration rollers during the assistant operation. The assistant operation is finished before a trailing edge of the print sheet being fed out from the sheet supply side-tray has passed through the primary supply rollers.